Bovine respiratory disease has been identified as an economically relevant trait which lacks selection tools to reduce post-weaning incidence. The lack of sufficient field morbidity data has been a major obstruction to development of tools for genetic improvement. The objective of this study was to investigate the genetic associations among real-time carcass ultrasound measures and probability of treatment for Bovine respiratory disease. Phenotypes of 2,870 crossbred steers were collected over two years (1,551 in year 1; 1,319 in year 2). The ultrasound measurements were collected at 3 times during the feeding period: receiving (day 0), processing 2 (80 days) and processing 3 (150 days). Ultrasound measurements included ribeye area, backfat thickness and percent intramuscular fat. Morbidity data were collected over the entire 240-day feeding period and classified as a binary observation, 1 for treated and 0 for non-treated, respectively.

* Morbidity had a negative genetic correlation with all ultrasound measurements.

* The genetic correlations with the greatest magnitude were between morbidity and ultrasound ribeye area, ultrasound backfat thickness and ultrasound percent intramuscular fat taken at receiving of -0.15, -0.58 and -0.11, respectively.

These results imply those individuals with smaller ribeye area and less backfat upon arrival to the feedlot have the highest probability of suffering from a Bovine respiratory disease incidence.

Source: University of Arkansas Division of Agriculture

Brigham et al., 2010. Colorado State University, University of Missouri, West Texas A&M University, University of Illinois, South Dakota State University and Cornell University